1. Technical Field
The present invention relates generally to the delivery of Q-switched high power laser pulses for purposes of medical treatment. More specifically, the invention relates to a method and apparatus for use with a biomicroscope which permits high power laser pulses to be focused coincident with the center line and focus of the biomicroscope while protecting the eyes of the biomicroscope observer.
2. The Prior Art
There has been increasing interest in the possibility of applying high power pulsed laser energy to tissue for the purpose of treating various diseases. In such systems, use is made of the very small focal diameter of laser beams to achieve high power density in the target tissue. A requirement of the laser delivery portion of the system is that the focused beam must be delivered coincident with the center of the field of observation of a biomicroscope. This is particularly important in the treatment of ocular tissue where the area to be treated may be no larger than one hundred and fifty micrometers in diameter. When high power laser pulses are applied to this tissue, an error in the application site of 0.1 millimeters can result in undesirable damage to adjacent tissue instead of beneficial alteration of the target tissue. The treating physician must therefore be able to predict, with a high degree of accuracy, where the pulse of energy will intersect the tissue. Prior art biomicroscopes allow adequate observation of sites to be treated; however, the problem which has been encountered is to couple high energy laser pulses to the observation system so that the focal point and the center of the observation system coincide with the focal point of the laser pulse. Once this has been done, there remains the problem of simply and effectively protecting the eyes of the observer from the high power laser pulses.
Another problem with systems of the type described relates to mobility. Mobility is an important feature of these systems, particularly where they are intended for ocular treatment. It is desirable that the system be readily transportable anywhere in a hospital or other medical facility.
It is to be noted that the present invention, when applied to surgery in the eye, relates to surgical procedures performed anterior of the retina and using high energy laser pulses. This is to be distinguished from photo coagulation procedures performed on the retina with low power CW (continuous wave) lasers such as described in U.S. patent application Ser. No. 06/239,015, now U.S. Pat. No. 4,397,310 filed February 27, 1981 by Oleg Pomerantzeff and assigned to the same assignee as is the present invention. In the Pomerantzeff system, the lower power CW laser is brought to focus at the nodal point of the patient's eye, a feature which cannot be employed with high power lasers for fear of damage to the eye. Moreover, in the Pomerantzeff system an ophthalmoscopic lens creates an aerial image of the fundus which is observed, illuminated and treated; such aerial images should be avoided in high power laser systems because focusing such lasers in air degrades the quality of the surgical beam. In addition, the use of low power lasers in the Pomerantzeff system does not require that the eyes of the observer be protected.